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R Ducrocq

Publications and source records attributed to R Ducrocq.

54 records · Page 3Linked to original sources
PubMed1992

[HbD Iran-beta-thalassemia association in a Tunisian family].

A nine-year-old boy from Béjà (North-Western Tunisia) was found to have both HbD Iran and beta-thalassemia. This patient presented with anemia and slight enlargement of the spleen and had a history of acute episodes of hemolysis. Structural studies on this hemoglobin variant used several miniaturized techniques, mainly carboxy-methyl-cellulose chromatography, reverse-phase high performance liquid chromatography and manual peptide sequencing using Chang's technique. The glutamic acid in position 22 on the beta chain was found to be replaced by a glutamine, establishing the diagnosis of HbD Iran. Concomitant presence of a thalassemia trait was suggested by the finding in the index patient of microcytosis, hypochromia and increased HbA2. The family study confirmed this patient's combined heterozygous anomalies, showing the D trait in the father and the beta thalassemia trait in the mother. The same combination was found in the index patient's sister who was, however, free of clinical symptoms. The explanation of this difference in clinical expression was provided by the ADN study which disclosed deletion of an alpha gene in the girl. The resulting alpha chain deficiency counterbalanced the beta chain deficiency.

Amino Acid Sequence↗
PubMed1991

Nucleotide sequence evidence of the unicentric origin of the beta C mutation in Africa.

The origin of the beta C mutation was studied by characterizing nucleotide sequence polymorphisms on beta C chromosomes of patients from various African countries. In the majority of cases, the beta C mutation was found in linkage disequilibrium with a single chromosomal structure as defined by classical RFLP haplotypes, intergenic nucleotide sequence polymorphisms immediately upstream of the beta-globin gene, and intragenic beta-globin gene polymorphisms (frameworks). In addition, three atypical variant chromosomes carrying the beta C mutation were observed, and are most probably explained either by a meiotic recombination (two cases) or by one nucleotide substitution occurring in an unstable array of tandemly repeated sequences (one case). These data demonstrate the unicentric origin of the beta C mutation in central West Africa, with subsequent mutational modification in a small number of instances. The data also supports gene flow of the beta C chromosome from subsaharan Africa to North Africa.

Africa↗
PubMed1989

Haplotypes in tribal Indians bearing the sickle gene: evidence for the unicentric origin of the beta S mutation and the unicentric origin of the tribal populations of India.

To determine the origin of sickle cell anemia (SS) in India, we analyzed haplotypes of the beta gene cluster in beta S-carrying individuals belonging to tribal populations living in the Nilgiris region of southern India and complemented the available data on tribes of east-central India. We found that in the Nilgiris tribes chromosomes bearing the beta S gene are linked in 91% of the cases to the "Asian" (Arab-Indian) haplotype (although 25% of the haplotypes had the epsilon polymorphic site negative, making the 5' portion of the haplotype identical with the African Senegal haplotype). These XmnI (+) chromosomes were associated with high G gamma expression (67.2 +/- 5.9%) and a high percentage of Hb F (15.5 +/- 7.9%; range, 6-25.3%). We have similar findings for tribal groups from west-central India (Gujarat). In east-central India we have confirmed the data of others, finding the same haplotype linked to beta S in tribes living in the east (Orissa, Andhra Pradesh). We conclude that the beta S gene in presently isolated and disperse tribal populations in India is associated with one predominant typical haplotype, suggesting a unicentric origin of the mutation in India. In addition, this finding implies a unicentric origin of the tribal populations themselves: The gene must have arisen and spread before tribal dispersion. Furthermore, we find extremely high frequencies of the (-alpha) haplotype in the Nilgiris (0.89) and in Gujarat (0.95). The beta S gene linkage to a high Hb F-expressing haplotype and the high incidence of alpha-thalassemia predict a mild phenotypical expression of sickle cell anemia in India.

Anemia, Sickle Cell↗
PubMed1988

Analysis of ligand-binding data without knowledge of bound or free ligand molar concentration.

A method is proposed to set the parameters in a nonlinear regression procedure to determine the equilibrium dissociation constant (Kd) and the high affinity receptor concentration (Bmax) of systems consisting of one ligand, one high affinity receptor, and n low affinity binding sites. This method is suitable when neither bound or free ligand formal concentrations nor the maximum of the binding signal can be deduced from the experimental data. The method makes use of (i) the abscissa of the first inflection point of the plot of any signal proportional to the binding of ligand to receptors versus the logarithm of the total ligand concentration, and (ii) the initial slope of the saturation curve plotted in direct coordinates. We first demonstrate that when such an inflection point exists, its abscissa lies between Bmax/2 + Kd(1 + d) and Bmax + 2Kd(1 + d), where d is a parameter representative of the binding to the low affinity sites. Second, we demonstrate that the initial slopes of two saturation curves in direct coordinates, where Bmax varies by a known factor, allows an estimation of the Bmax/Kd ratio, within certain limits. From these two sets of data it is subsequently possible to define a precise window for the values of both Bmax and Kd. The performance of the method has been evaluated in representative cases using Monte Carlo studies. The results establish conditions for the existence of an inflection point as well as the influence of low affinity binding, whether or not proportional to Bmax.

Binding Sites↗
PubMed1987

Measurement of glycated albumin in diabetic patients by biospecific affinity chromatography.

The percentage of glycated plasma albumin was measured by a procedure involving ammonium sulphate precipitation and Affi-Gel-Blue and phenylboronate chromatographies. The value correlates well with the amount of ketoamine-bound sugars determined by colorimetric assay (r = 0.98, n = 39). The normal mean value is 3.9 +/- 0.3% (mean +/- S.D., coefficient of variation = 7.7%, n = 32) and varies from 3.9 to 21% in diabetics (n = 54). A good correlation is found with the mean blood glucose value of the preceding twenty days (r = 0.92, n = 57). Because of its relative ease of determination, glycated albumin constitutes a good short-term glycemic index and an alternative to glycated haemoglobin in some specific cases.

Blood Glucose↗
PubMed1984

Haemoglobinopathies: a pitfall in the assessment of glycosylated haemoglobin by ion-exchange chromatography.

Total glycosylated haemoglobin was determined by a minicolumn ion-exchange chromatography technique (Bio-Rad) and correlated with the mean of fasting and post-prandial blood glucose values for the preceding 6 weeks. In 360 diabetic subjects, free of congenital haemoglobinopathies and other detected causes of haemoglobin A1 misinterpretation (reference diabetic group), a highly significant correlation was established between haemoglobin A1 and glucose (y = 0.54 X +4.91; r = 0.791; p less than 0.01). In 28 of the 29 patients with heterozygous haemoglobinopathies (HbS, C, D, E), the apparent haemoglobin A1 values were lower than expected according to the 95% confidence limits of the diabetic reference group. The apparent haemoglobin A1 value was above these limits in patient 29, with beta thalassaemia. Patients with inappropriate glycosylated haemoglobin values should be investigated for causes of haemoglobin A1 misinterpretation, in particular, haemoglobinopathies.

Blood Glucose↗
PubMed1984

Haemoglobinopathies, malaria, and other interferences with HBA1 assessment.

Total glycosylated haemoglobin (HbA1) was determined by a rapid minicolumn chromatography technique in 438 diabetic patients and correlated with the mean of fasting and post-prandial blood glucose values for the preceding six weeks. In 360 of them, free of congenital haemoglobinopathies and other detected causes of HbA1 mis-interpretation (reference group), a significant correlation was established between the HbA1 and glucose values: y = 0.54 X + 4.91; r = 791; (p less than 0.01). In 28 of the 29 patients with heterozygous haemoglobinopathies (Hb S = 17; Hb C = 8; Hb D Pundjab = 1; Hb E = 2) the apparent HbA1 values were inappropriately low. The apparent HbA1 value was above the 95% confidence limits in the 29th patient, with beta thalassaemia. In 10 out of 14 diabetics with recurrent hypoglycemic attacks, the HbA1 value was lower than the 95% confidence limits of expected values. Out of 21 diabetics with a shortened red cell lifespan (occult blood losses: 10; haemolysis: 11) 15 displayed a lower than expected HbA1 value. Among these was a diabetic patient with malaria and severe anaemia. Out of 14 diabetics with severe chronic renal failure only 3 presented with apparent HbA1 values above the 95% confidence limits.

Adult↗
PubMedDate not supplied

Short insertion in a hemoglobin chain: Hb Esch, an unstable alpha1 variant with duplication of the sequence Ala65-Leu-Thr-Asn68.

Hemoglobin (Hb) Esch, is an alpha1 variant, expressed at less than 5%, resulting from the duplication of the 12 nucleotides corresponding to CD65 through 68. The effect of this insertion is the repetition of the sequence Ala-Leu-Thr-Asn, which corresponds to the last turn of helix E. In this variant the presence of a one-turn elongated helix E causes instability and increased ligand affinity. Hb Esch was characterized by DNA sequencing and confirmed by electrospray mass spectrometry. Functional studies were performed by flash photolysis measurements on a fraction isolated by flatbed isoelectric focusing, which was enriched in the abnormal hemoglobin. Similar to other alpha chain variants due to short insertion (or deletion), Hb Esch probably results from a slipped mispairing mechanism. The stability of such modified proteins depends upon the region which is added or deleted and usually is more stable when involving a flexible loop or complete helix turn(s) near by.

Adult↗
PubMedDate not supplied

Three-year follow-up of hydroxyurea treatment in severely ill children with sickle cell disease. The French Study Group on Sickle Cell Disease.

PURPOSE: To observe the safety and efficacy of hydroxyurea (HU), a drug that stimulates fetal hemoglobin (Hb F) production, in previously severely ill children with sickle cell disease. PATIENTS AND METHODS: HU was given in an uncontrolled study to 35 children with sickle cell disease, aged from 3 to 20 years, suffering from frequent painful crises. Mean duration of treatment was 32 months (range: 12-59 months). RESULTS: HU induced an increase in Hb F levels in all children out one; this increase was maximal after 9 months of treatment, was largely sustained thereafter, and was related to HU dose and inversely to patients' age. We also noted an apparent reduction in crisis, which occurred principally after 3 months of therapy and did not seem strictly correlated with the rise in Hb F level. No serious hematopoietic complication was observed. Growth curves and sexual development were not modified. CONCLUSION: Our data support the efficacy of HU in reducing painful events in children with sickle cell disease. Short- and middle-term tolerances are good. Thus, we think that HU can be given to children affected by frequent and severe painful crises. We recommend, however, very cautious use of this drug, because its long-term effects in children are still unknown.

Adolescent↗
PubMedDate not supplied

Measurement of adult hemoglobin in fetal blood samples by high-performance liquid chromatography as purity control for the prenatal diagnosis of chromosomal abnormalities.

This study was aimed at testing if measurement of adult hemoglobin (HbA) by ion exchange high-performance liquid chromatography could serve as a purity control of fetal blood samples. We studied 240 samples obtained for karyotyping by cordocentesis under ultrasound guidance. Mean red cell volume (MCV), red cell distribution width (RDW) and HbA were measured on each sample. HbA was determined from 5 microliters of blood in 8 min. From 18 to 30 weeks of gestation, HbA values in fetal blood do not vary and are tightly clustered around 5.4% (SD:1.1%). After 30 weeks, HbA increases as the fetal to adult switch begins. Experimental contaminations of fetal blood by maternal blood show that HbA variations are more pronounced than MCV or RDW variations. A 5% contamination is readily detected. This approach is rapid, sensitive and reliable. Incidentally, it readily detects the presence of an abnormal hemoglobin.

Chromatography, High Pressure Liquid↗
PubMedDate not supplied

Two fetal hemoglobin variants affecting the same residue: Hb F-Emirates [G gamma 59(E3)Lys-->Glu] and Hb F-Sacromonte [G gamma 59(E3)Lys-->Gln].

Two fast-moving fetal hemoglobin variants were discovered in hematologically normal newborn babies; the first originated in the United Arab Emirates and the second in France. The structural study, carried out by miniaturized techniques of protein chemistry, showed that these two mutations affected the same residue of the G gamma chain, the lysine at position 59(E3) was replaced by glutamic acid in Hb F-Emirates, and by glutamine in Hb F-Sacromonte.

Amino Acid Sequence↗
PubMedDate not supplied

Determination of Hb F levels: the routine methods.

The two classical methods used to determine the level of Hb F in a hemolysate are herein described. Measurement of this hemoglobin fraction by resistance to alkali denaturation was the first technique introduced; it is today largely replaced by ion exchange high performance liquid chromatography. The limits, pitfalls, and advantages of the two methods are discussed.

Alkalies↗
PubMedDate not supplied

Gamma chain heterogeneity: determination of Hb F composition by perfusion chromatography.

The Ggamma:Agamma ratio is around 70:30 at the time of birth and usually 40:60 in the trace amounts of Hb F found in the adult. Changes in this ratio are observed in several hemoglobin disorders providing insights on the genetics and molecular pathophysiology of these diseases. Several techniques have been proposed to measure the Ggamma:Agamma ratio. We here describe perfusion chromatography which is now in routine use in one of our laboratories. The method involves a high velocity flow of the mobile phase through a porous reversed phase chromatographic stationary bed and allows us to determine this parameter one order of magnitude faster than with conventional high performance liquid chromatography.

Chromatography↗
PubMedDate not supplied

[Good practices for the study of hemoglobin].

Hemoglobinopathies have become a significant national health problem in France. The biologists have a pivotal role in the genetic diagnoses. Although sickle cell disease (SCD) is the most frequent abnormality found: not less than 200 new cases are observed each year at birth, many other globin gene variations are found in the various ethnic groups. Since 1995 a neonatal sickle cell screening program has been established for at risk newborns. This programme is supported by the "Association française de dépistage et prévention des handicaps de l'enfant" (AFDPHE). The characterization of hemoglobin genetic variations requires a comprehensive set of laboratory techniques for which we specify here main clinical and technical recommendations.

Blood Chemical Analysis↗